Merged PR 2522: Don't Repeat Yourself for KPIs - Applied to Bookings

# Description

What's new:
- Creation of `get_kpi_dimensions`: new macro to have a single point of source of configuration for dimensions for the KPIs. It's a way to enforce global variables on-demand. I kind of like this approach and we could do it for Xero models as well :)
- Modification of `int_core__mtd_booking_metrics` and `int_dates_mtd_by_dimension`: removal of duplicated code within the dimension context. Uses Jinja code and applies different configurations depending on the dimension chosen. Still, different metrics are placed in different CTEs. I believe it might be possible to also configure metrics BUT at the cost of over-complexifying the macro logic, so I wouldn't go for it at this stage.

# Checklist

- [X] The edited models and dependants run properly with production data.
- [X] The edited models are sufficiently documented.
- [X] The edited models contain PK tests, and I've ran and passed them.
- [X] **I have checked for DRY opportunities with other models and docs.**
- [X] I've picked the right materialization for the affected models.

# Other

- [ ] Check if a full-refresh is required after this PR is merged.

Related work items: #19325

models/intermediate/cross/int_dates_mtd_by_dimension.sql

@@ -1,4 +1,6 @@
 
+{% set dimensions = get_kpi_dimensions() %}
+
 {{ config(materialized="table", unique_key=["date", "dimension", "dimension_value"]) }}
 
 with
@@ -7,32 +9,24 @@ with
     ),
     int_dates_mtd as (select * from {{ ref("int_dates_mtd") }})
 
-select distinct
-	d.year,
-	d.month,
-	d.day,
-	d.date,
-	'global' as dimension,
-	'global' as dimension_value,
-	d.first_day_month,
-	d.last_day_month,
-    d.is_end_of_month,
-    d.is_current_month
-from int_dates_mtd d
-
-union all 
-
-select distinct
-	d.year,
-	d.month,
-	d.day,
-	d.date,
-	'by_number_of_listings' as dimension,
-	a.active_accommodations_per_deal_segmentation as dimension_value,
-	d.first_day_month,
-	d.last_day_month,
-    d.is_end_of_month,
-    d.is_current_month
-from int_dates_mtd d
-inner join int_core__mtd_accommodation_segmentation a
-on d.date = a.date
+{% for dimension in dimensions %}
+    select distinct
+        d.year,
+        d.month,
+        d.day,
+        d.date,
+        {{ dimension.dimension }} as dimension,
+        {{ dimension.dimension_value }} as dimension_value,
+        d.first_day_month,
+        d.last_day_month,
+        d.is_end_of_month,
+        d.is_current_month
+    from int_dates_mtd d
+    {% if dimension.dimension == "'by_number_of_listings'" %}
+        inner join int_core__mtd_accommodation_segmentation a
+		on d.date = a.date
+    {% endif %} 
+    {% if not loop.last %}
+        union all
+    {% endif %}
+{% endfor %}